Half life 2 is a Valve made game. And seeing as Valve does games right *cough cough* Team Fortress 2 *cough cough* it can't go wrong.
If you like first person shooters, minor puzzle solving, beating the living bujeezus out of your enemys' croches using a crowbar, handling an RPG, shooting an RPG at giant gunships, zombies, and basically just sci-fi stuff, then try this game out. While it is $10 (which in my opinion it should be cheaper, because come on! This game was made in 2004 and it's 2015 as of writing this!), it is still worth it. There are even some good mods for it out there.
I highly recommend this game. While I may have a low hour count compared to other reviewers. Well, I've been playing a community made mod that is pretty much the same as this, with some minor enhancements and bug fixes.